The present invention relates generally to satellite-based communication systems, and more particularly, to network architectures that provide for a low earth orbit and geosynchronous orbit satellite-based communications systems.
Currently, there are geosynchronous orbit satellite communication systems such as the Brazilsat system, for example, that provide fixed wide area communication (telephony) services. There are also low earth orbit satellite communication systems such as the GlobalStar and Iridium systems, for example, that provide mobile communication (telephony) services. However, heretofore, the fixed and mobile systems have not been coupled together to provide an integrated system. The present invention addresses this issue.
Accordingly, it is an objective of the present invention to provide for network architectures for low earth orbit and geosynchronous orbit satellite-based communications systems.
To accomplish the above and other objectives, the present invention is network architectures that provide telephony service for fixed and mobile satellite ground terminals using code division multiple access (COMA) access technology. The network architectures were developed to provide telephone service in areas of the earth that have relatively little or no land-based communication infrastructure, such as underdeveloped rural areas, for example.
The communications network architectures comprise a geosynchronous satellite operating in the fixed satellite service (FSS) band communications system including a geosynchronous communications satellite and a low earth orbit satellite communications system including a plurality of low earth orbit communications satellites. A low earth orbit gateway comprising a terminal is used to communicate with the low earth orbit communications satellites using multiple access communication channels. A geosynchronous gateway comprising a terminal is used to communicate with the geosynchronous communications satellite by overlaying multiple access communication channels onto fixed channel assignments and transmitting the overlayed channel assignments. The terminals in the geosynchronous and low earth orbit gateways communicate with a public switch telephone network (PST). A fixed terminal having a handset is used to selectively communicate with the low earth orbit communications satellite using the multiple access communication channels, or with the geosynchronous communications satellite by extracting the multiple access communication channels from the fixed channel assignments.
The LEO gateway communicates by way of the low earth orbit communications satellites to fixed terminals located at low telephone density sites or that can be part of a clustered village phone systems, for example. The LEO satellite communications system also has mobile terminals that are used by individuals in vehicles. The mobile terminals typically interface to the LEO communications satellites and to cellular sites in high telephone density areas. Thus, the mobile terminals may be used in both low and high telephone density areas. The mobile terminals interface by way of the cellular sites or LEO communications satellites and LEO gateway to the public switch telephone network.
Each communication site in the low telephone density areas has a fixed terminal and a public use handset that are used to communicate with both the geosynchronous communications satellite and the LEO communications satellites. Each clustered village phone system has a very small aperture terminal (VAST) that is coupled to either a wired or wireless loop interconnecting a plurality of conventional telephones. The very small aperture terminal also has a public use handset for backup purposes, in case of failure of the wired or wireless loops.
The present invention preferably uses code division multiple access (CDMA) communication technology in the fixed satellite service (FSS) band. The CDMA technology allows the fixed terminals to communicate with both the geosynchronous and LEO communications satellites. The present invention preferably uses GlobalStar terminals, handsets and gateway technology in conjunction with the fixed satellite service geosynchronous satellite to provide rural telephony. Thus, the capabilities of the GlobalStar system are expanded by the present invention to support fixed satellite service telephony traffic.
The present invention provides for a shared GEO and LEO telephony service gateway. The present invention uses low cost fixed and mobile satellite terminals. The architecture of the present invention provides for a scalable telephony solution that allows from one to several hundred users per clustered village terminal.